3.0-stable review patch. If anyone has any objections, please let us know.

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From: Alex Deucher <alexander.deucher@amd.com>

commit 5a6e8482a16e61250a9121fc9ec719ab0529e760 upstream.

FB scratch indices are dword indices, but we were treatingthem as byte indices. As such, we were getting the wrongFB scratch data for non-0 indices. Fix the indices andguard the indexing against indices larger than the scratchallocation.

Fixes memory corruption on some boards if data was writtenpast the end of the FB scratch array.